1. Field of the Invention
The present invention relates to a subsea pipeline direct electric heating (DEH) cable, so called “piggyback” cable.
2. Description of the Related Art
For heating of oil or gas pipelines in order to prevent hydrate and ice formation on the pipeline walls, a common practice consists in developing a direct heating system based on a current supply cable which is traditionally made simultaneously with the laying of the pipeline. In a general way a piggyback cable is strapped to the pipeline during installation thereof.
Piggyback cables are well known and have been already disclosed in patents. For instance, referring to FIG. 1, which is a cross section view of a piggyback cable described in WO2007096775, a piggyback cable 1 comprises a copper conductor 2 with a standard triple extruded insulation system: conductor screen 3 (semi-conductive), cross-linked polyethylene insulation 4, and insulation screen (semi-conductive) 5. A steel tube 6 which is containing optical fibers is performed into a sinus shape in order to achieve required bending properties, and is placed onto the insulation screen 5. One or more semi-conductive sheath(s) 7 is (are) extruded over this assembly.
Some of the piggyback cables disclosed in prior art documents, may also have a protective system to take up limited either radial or axial loads, or may have a limited resistance to impact and crush loads with a large outer diameter.